Steady-State Design and Economical Analysis

DMSO is a better entrainer for this system. In the following, the economic optimal design flowsheet of this IPA dehydration process when using DMSO as the entrainer wUl be established to minimize the TAC of the overall process. 

It is worth mentioning that, apart from the important factors above relating to the phase equilibrium behavior, other factors such as thermally stable, nontoxic, low price, and other physical properties should also be considered in the entrainer selection. A good paper by Gmehling and Mollmann used four examples to demonstrate the entrainer selection procedure for extractive and azeotropic distillation. 

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Some recent applications have benefited from advances in computing and computational techniques. Steady-state simulation is being used off-line for process analysis, design, and retrofit process simulators can model flow sheets with up to about a million equations by employing nested procedures. Other applications have resulted in great economic benefits these include on-line real-time optimization models for data reconciliation and parameter estimation followed by optimal adjustment of operating conditions. Models of up to 500,000 variables have been used on a refinery-wide basis. 

The area of reactor design has been widely studied, and there are many excellent textbooks that cover this subject. Most of the emphasis in these books is on steady-state operation. Dynamics are also considered, but mostly from the mathematical standpoint (openloop instability, multiple steady states, and bifurcation analysis). The subject of developing effective stable closedloop control systems for chemical reactors is treated only very lightly in these textbooks. The important practical issues involved in providing reactor control systems that achieve safe, economic, and consistent operation of these complex units are seldom understood by both students and practicing chemical engineers. 

It should be noted that these questions do not fit comfortably within any of the conventional categories of operability analysis, such as controllability (regulatory capability about a steady state), switchability (ability to switch between operating modes), flexibility (ability to accommodate uncertainty at steady state), and robust control (ability to maintain stability and performance of a control scheme despite perturbations in the characteristics of the controlled system). Rather, we attempt to develop an integrated design approach that allows us to consider operability issues on a par with economic issues, thus permitting design and synthesis decisions to be made within a common framework. 

Space 6. Behavior analysis steady state simulations are carried out to explore the kinetics, gas/liquid mass transfer, hydrodynamics and multiplicities inside the units. Dynamic simulations are performed to check the robustness of the design, in terms of the ability to maintain product purities and conversion in a desired range when disturbances occur. If the process is controllable and economically attractive at the estimated operating conditions, go to the next... 

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